Abstract

In the present investigation we analyze the Stark broadened profile of the He II Balmer-α transition at densities up to
and temperatures up to
The experimental spectra have been recorded with the aid of an argon or nitrogen flushed spectrograph for the visible spectral range and a high resolution grating. The plasma of a gas-liner pinch is accurately diagnosed by Thomson scattering. We compare the experimental spectra with theoretical ones calculated according to the Frequency Fluctuation Model (FFM) and find excellent agreement of the profiles in the whole measured
spectral range when ion dynamics is taken into account. The experimental values of the width agree well with existing experimental data from reliable experiments. Calculations according to the Model Microfield Method (MMM) underestimate the width and the standard theory does not give the experimental density dependence. Concerning the shift, the present experimental values are consistent with existing shifts measured at lower temperatures but cannot favor calculations according to MMM or the standard theory which differ by a factor of two. New calculations have to be performed and compared with experimental data so that the contributions of the different red and blue shifts are properly accounted for to enable a density diagnostics using the shift of the spectral lines.